Why then only one star ???
Because Parallels runs a rogue update policy !!!
After every major Mac update is a new update for Parallels due 49 brings the few new features.
Previous versions are no longer maintained by Paralles and were not compatible in both Lion and at Mavericks update.
Since this type. Notice only after a MacOS update, you are forced to buy the update if you want to get to your Windows data under Parallels.
Therefore, Parallels is a rogue update the event!
The purchase price is likely to be understood as Abonement depending on date of purchase for 1-2 years.
Plan additional annual 49 on the purchase of Parallels Updates for one.